Catherine P. Browman

Articulatory gestures as phonological units

We have argued that dynamically defined articulatory gestures are the appropriate units to serve as the atoms of phonological representation. Gestures are a natural unit, not only because they involve task-oriented movements of the articulators, but because they arguably emerge as prelinguistic discrete units of action in infants. The use of gestures, rather than constellations of gestures as in Root nodes, as basic units of description makes it possible to characterise a variety of language patterns in which gestural organisation varies. Such patterns range from the misorderings of disordered speech through phonological rules involving gestural overlap and deletion to historical changes in which the overlap of gestures provides a crucial explanatory element. Gestures can participate in language patterns involving overlap because they are spatiotemporal in nature and therefore have internal duration. In addition, gestures differ from current theories of feature geometry by including the constriction degree as an inherent part of the gesture. Since the gestural constrictions occur in the vocal tract, which can be charactensed in terms of tube geometry, all the levels of the vocal tract will be constricted, leading to a constriction degree hierarchy. The values of the constriction degree at each higher level node in the hierarchy can be predicted on the basis of the percolation principles and tube geometry. In this way, the use of gestures as atoms can be reconciled with the use of Constriction degree at various levels in the vocal tract (or feature geometry) hierarchy. The phonological notation developed for the gestural approach might usefully be incorporated, in whole or in part, into other phonologies. Five components of the notation were discussed, all derived from the basic premise that gestures are the primitive phonological unit, organised into gestural scores. These components include (1) constriction degree as a subordinate of the articulator node and (2) stiffness (duration) as a subordinate of the articulator node. That is, both CD and duration are inherent to the gesture. The gestures are arranged in gestural scores using (3) articulatory tiers, with (4) the relevant geometry (articulatory, tube or feature) indicated to the left of the score and (5) structural information above the score, if desired. Association lines can also be used to indicate how the gestures are combined into phonological units. Thus, gestures can serve both as characterisations of articulatory movement data and as the atoms of phonological representation.

Towards an articulatory phonology

We propose an approach to phonological representation based on describing an utterance as an organised pattern of overlapping articulatory gestures. Because movement is inherent in our definition of gestures, these gestural ‘constellations’ can account for both spatial and temporal properties of speech in a relatively simple way. At the same time, taken as phonological representations, such gestural analyses offer many of the same advantages provided by recent nonlinear phonological theories, and we give examples of how gestural analyses simplify the description of such ‘complex segments’ as /s/–stop clusters and prenasalised stops. Thus, gestural structures can be seen as providing a principled link between phonological and physical description.

Papers in Laboratory Phonology: Tiers in articulatory phonology, with some implications for casual speech

A fluid fitting for attaching fluid conduits to a housing which makes possible a simplified assembly procedure that requires only the insertion of a tube assembly into a preassembled nut located in a threaded opening in the housing. The assembly includes an expandable clip located on the tube between retainer beads formed on the tube. The clip contains locking fingers that engage a shoulder on the nut.

Some Notes on Syllable Structure in Articulatory Phonology

Two approaches to seeking stable patterns in the gestural organization of speech are examined: local organization (individual gestures coordinated with other individual gestures) and global organization (gestures forming larger conglomerates). Articulatory evidence from American English words with a variety of initial consonants and clusters shows that syllable-initial consonants form a global organization (indexed by a metric we term the C-center) that is coordinated with the syllables vowel gesture. For syllable-final consonants, however, the evidence suggests that a local organization is employed: The first postvocalic consonant gesture is coordinated with the vowel gesture. Implications of these different styles of organization for the perceptual and phonological structure of speech are discussed.

Articulatory synthesis from underlying dynamics

We are testing a model of articulatory coordination and control over time using an articulatory synthesizer (ASY) that converts time‐varying specifications of articulator positions into speed [Rubin, Baer, and Mermelstein J. Acoust. Soc. Am. 70, 321–328 (1981)]. These articulator specifications are now generated from an underlying dynamical model that defines a particular linguistic event. Coordination among individual articulators emerges from this model, as does the time course of the event. No point‐by‐point temporal control is required. Synthesis will allow perceptual evaluation of different underlying dynamical models. [Work supported by NIH and ONR.]

Lexical organization and Welsh consonant mutations

Abstract The role of phonological form in the lexical organization of morphologically related words is investigated using consonant mutations in Welsh. Consonant mutations are a regular form of nonaffixal morphology, in which the initial consonant of a word changes depending on its syntactic context; for instance, the word pont “bridge” may appear as bont or font . In English, it has been shown that affixal variants, such as POUR-POURED, prime each other strongly, while nonaffixal variants, such as HUNG-HANG, show weak or nonexistent priming ( S. T. Kempley & J. Morton (1982) British Journal of Psychology , 73 , 441–454; R. F. Stanners, J. J. Neiser, W. P. Hernon, & R. Hall (1979) Journal of Verbal Learning and Verbal Behavior , 18 , 399–412). Using the task of auditory repetition priming, we show that mutation is similar to affixing in English in that mutated variants prime each other. We further show that abstract morphological categories, rather than identity of phonological form, are required to organize the Welsh lexicon, thus suggesting that current phonologically based lexical models need to be revised. An alternative model utilizing an underspecified autosegmental representation is proposed.

Task‐dynamic modeling of interarticulator coordination

Speech production involves the formation and release of constrictions at different points in the vocal tract. Progress is reported on a task‐dynamic computational model of autonomous coordination among the components of articulatory synergies (e.g., lips and jaw) that participate in motions along functionally defined tract variables (e.g., lip aperture and protrusion). For each speech gesture, a time‐invariant dynamical system (damped, second‐order) is specified at the tract‐variable level, and is transformed into a gesturally and posturally specific dynamical system for the synergy components. Articulatory movement patterns emerge as implicit consequences of the gesture‐specific tract‐variable control structures and the ongoing postural state of the articulators. Explicit trajectory planning is not required. Significantly, the modeled coordinative processes are exactly the same during simulations of unperturbed, mechanically perturbed, and coproduced speech gestures. All simulations are implemented using...

Modeling speech production using dynamic gestural structures

In the present computational model of speech production, an utterance is represented as an organization of primitive linguistic units, gestures, into a larger structure, a gestural score. Each distinct gesture is linked to a particular subset of vocal tract variables (e.g., lip aperture and protrusion) and model articulators (e.g., lips and jaw), and is associated with a set of time‐invariant dynamic parameters (e.g., lip aperture target, stiffness, and damping coefficients). The values of the dynamic parameters and their activation intervals are computed as part of the gestural score for a given utterance using a linguistic gestural model that includes a gesture‐based dictionary of English syllables and a flexible rule interpreter for manipulating dynamic parameters and inter‐gestural phasing. The gestural score serves as input to our task‐dynamic model of sensorimotor coordination. In this model, the evolving configuration of the model articulators results from the gesturally and posturally specific way...

Extracting dynamic parameters from articulatory movement

In order to model the movements of the speech articulators using a dynamical systems approach, it is necessary to specify (1) the specific form of the dynamical equation, (2) the portion of the articulatory trajectory being described/generated by the equation—the “window,” and (3) the values of the coefficients to be used in the equation. In this work, a damped mass‐spring dynamical system is assumed, as used in previous task dynamic modeling [Saltzman et al., J. Acoust. Soc. Am. Suppl. 1 82, S15 (1987)]. A program was developed to determine the values of the coefficients for the equations, using various definitions of the articulatory window. The program uses a nonlinear least‐squares algorithm to determine the best fit between the observed trajectories and the trajectories generated using a range of values for the coefficients. This program is currently being tested on simulated data with known parameters in order to establish the accuracy and limitations of the procedure. There will be a report on the ...

Applying the program NEWPAR to extract dynamic parameters from movement trajectories

In a model of articulatory movement, based on a dynamical systems approach, parameter values derived from actual articulatory data are being used. One way of obtaining these values relies on the program NEWPAR, which has been developed to analyze articulatory movement in order to extract dynamic parameters such as frequency that will serve as coefficients in the model equation [McGowan et el., J. Acoust. Soc. Am. Suppl. 1 83, S113 (1988)]. Alternative hypotheses for the application of NEWPAR have been tested, including starting the half‐cycle windows at different points in the trajectory and fixing either the initial displacement and velocity or the initial and final displacement as a means of reducing the number of parameters to be fitted. Tests have been made on simulated data, consisting of sinusoidal curves with damping varied from completely undamped to critically damped. Patterns in the results of these tests and some preliminary analyses of actual lower lip movement trajectories will be shown. [Wor...